The present invention relates to a braking apparatus for speed-reduction or stop control of an electric vehicle driven by the power from a battery.
There is known an electric vehicle of the type that electrical energy from an external power source is supplied to a vehicle-mounted battery for charging the battery, and the vehicle is driven with the charged energy. For example, a braking apparatus for an electric-powered vehicle is disclosed in JP,A, 1-126103 as a braking apparatus for speed-reduction or stop control of such an electric vehicle. In this braking apparatus for an electric-powered vehicle, a mechanical braking force and an electrical braking force are applied to surely speed down or to stop the vehicle. Alternatively, in the braking apparatus, the mechanical braking force is controlled so that the sum of the mechanical braking force and the electrical braking force becomes a commanded braking force, and the regenerative energy due to the electrical braking force is effectively supplied to a battery.
Also, a motor controller for an electrically driven vehicle disclosed in JP, A, 1-252102 is arranged such that, while the vehicle is traveling at a high speed, regenerative braking is effected upon a service brake being actuated by a brake pedal, thereby increasing a braking performance.
A slip determining device and a traction controller for a battery vehicle is disclosed in JP,A, 3-60302. In this traction controller, a traveling motor is controlled so that tires do not slip at the time of start-up on slippery roads such as ones covered with snow. More specifically, a slip ratio of a vehicle road wheel is calculated and, based on the calculated slip ratio, the traveling motor is controlled so as to prevent the wheel from slipping.
In an electric car controller disclosed in JP, A, 4-150702, regenerative braking is subject to an anti-lock brake process when a driving wheel is brought into a locked state. In the anti-lock brake process, a slip ratio of the wheel is detected and, when the slip ratio is greater than a set value, a regenerative braking command is limited and the slip ratio is controlled to become smaller. When the slip ratio is smaller than the set value, a regenerative braking force is increased and the slip ratio is controlled to become larger.
In an electric vehicle with a regenerative braking function disclosed in U.S. Pat. No. 4,242,617, a rotary shaft of a traveling motor and a rotary shaft of an alternator coupled to each other through a control differential gear mechanism, and an output shaft of the control differential gear mechanism is coupled to wheels through a vehicular differential gear mechanism. While the vehicle is traveling, electric power from a battery is supplied to the traveling motor so that the traveling motor is driven to rotate the wheels. When stopping the vehicle, the supply of electric power to the traveling motor is stopped upon a brake pedal being tread on, and a field current depending on the tread amount of a brake pedal is supplied to a field winding of the alternator. The electric power produced by the alternator is supplied to the battery. When the tread amount of the brake pedal is increased, the traveling motor is stopped by a mechanical brake.
Other examples of the regenerative braking for an electric vehicle, similarly to the above one described in U.S. Pat. No. 4,242,617, are disclosed in U.S. Pat. Nos. 4,419,610 and 4,363,999.
As one example of a braking apparatus for vehicles driven by internal combustion engines rather than electric vehicles, there is also known an antiskid controller for a vehicular braking apparatus disclosed in U.S. Pat. No. 4,776,644. This antiskid controller is intended to prevent wheels of the vehicle from being locked. A wheel speed is detected by a wheel speed sensor and, when a deceleration of the wheel exceeds a preset value, the brake pressure is reduced. When the wheel deceleration becomes smaller than a preset value, the brake pressure is increased. The vehicle wheels are thereby prevented from being locked.
Other examples of a braking apparatus for vehicles driven by internal combustion engines are disclosed in U.S. Pat. Nos. 4,818,037 and 4,753,493.